Various factors of muscle growth

Various factors of muscle growth

Geschreven door Nathan Albers
Geschatte leestijd: 4 minuten

To achieve maximum results from your workouts, you need to consider several diverse factors of muscle growth. When you adhere to these principles, you can perform optimally and get the most out of your training sessions. Some of these factors of muscle growth include repetitions, the number of activated muscle fibers, hormone production, fluid balance in the muscle cells, and maximum muscle damage. We will discuss these factors extensively in this article.

factoren van spiergroei

The number of repetitions

The first factor of muscle growth we want to delve into specifically is the number of repetitions. When you start strength training and fitness, you may do 15 repetitions or more with relatively light weights. This is not entirely unwise for a beginner, as the muscles and tendons need to adapt to the movements and intensity. Additionally, the risk of injury is low if you perform high repetitions with low weights.

However, when you are advanced in fitness and have mastered the correct execution of fitness exercises, 15 repetitions or more are suboptimal if you want to achieve muscle growth. The weight used in 15 repetitions is often too low, resulting in low training load. This insufficiently trains the type II muscle fibers, which are the fibers that can achieve the most growth. If you perform many repetitions, you mainly train the type I muscle fibers, which are more resistant to fatigue but have limited growth capacity.

So, in summary: if you are new to the gym or planning to increase muscle endurance, then 15 repetitions or more may be beneficial for you. But do not expect a large increase in muscle mass as a result. The optimal number of repetitions for muscle growth is between 8 and 10 repetitions. However, eventually, this will also plateau your progress as your body becomes accustomed to it. Then it’s time to vary again.

If you want to learn more about muscle fibers, read our article on the different types of muscle fibers and their properties.

Maximally active muscle fibers

Another important principle of muscle growth is the number of available fibers that you activate in the muscles. When you perform a fitness exercise, initially, the small motor units are recruited. A motor unit consists of the nerve and the muscle fibers activated by the nerve. As you continue the fitness exercise, not only the small motor units but also the large motor units are recruited. When doing 8 to 10 repetitions, both small and large motor units are activated.

Hormone production

Thus, the number of repetitions has an undeniable impact on the number of muscle fibers and motor units you activate during exercises. But another effect of performing 8 to 10 repetitions is the effect on anabolic hormones such as testosterone in the body. Testosterone levels are higher, for example, at 8 to 10 repetitions than with longer sets. These hormones help muscles grow when exposed to a training stimulus. The more anabolic hormones you have in your body, the more muscle growth you will achieve.

In addition, lactic acid also plays an important role in this entire anabolic process. In the anaerobic glucose energy system, also known as the lactic acid system, a lot of lactic acid is released in the body. This energy system is the one that provides energy when you perform sets of 8 to 10 repetitions. If a lot of lactic acid is released in the body, the body’s hormonal response is also greater. If you train with fewer repetitions, you mainly use the phosphate system for energy and produce less lactic acid. The body’s hormonal effects on this lactic acid production persist for more than an hour after training.

Fluid balance in the muscles

Do you know the feeling of a pump in your muscles during or after training? This muscle pump occurs when plasma enters the space between the blood vessels and the muscle cells. This builds pressure and brings plasma into the muscles. This muscle pump is maximum when doing 8 to 10 repetitions and improves fluid balance in the muscles. This stimulates protein synthesis and prevents breakdown of muscle cells. If you do too few repetitions, the muscle is not sufficiently under tension, and a good pump is not developed. And all other benefits are less pronounced than when doing 8 to 10 repetitions.

Muscle damage

Finally, doing 8 to 10 repetitions can lead to higher damage to muscle cells. The number of muscle fibers you damage through training results in greater muscle growth. Here, you must consider the overload principle: muscles only grow when exposed to a load greater than they can handle. Due to this high intensity, they are exposed to a training stimulus greater than what the muscle cells are accustomed to, resulting in more muscle growth.

Till failure and past failure

Finally, a term you should often hear: Until failure, or shortly, ’till failure. Every time an article here or on Fitsociety talks about a desirable number of repetitions, it is assumed that this is actually the maximum number of repetitions you can do with the chosen weight!

Doing 8 to 10 repetitions will yield little to nothing if you could continue to 20 repetitions. Until failure means you continue repetitions until you really can’t do more. Thus, you are essentially at the point where you have maximally taxed the muscles. A good way to overtax them is to then go further, beyond failure. This is also called “forced repetitions.” You can do this by having someone assist you with the last repetitions (or yourself with a free arm or leg), or for example with drop sets (immediately continue with less weight after failure). Other methods include half repetitions, or “cheating” repetitions where you squeeze out a few more repetitions by using poorer technique. For example, by allowing your upper body to help at the end of a set of dumbbell curls. Normally, this is the last thing you want to do, but if you do it to do extra repetitions and don’t make dangerous movements, it’s a fine method.


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